There are two ways to integrate Adapty SDK: Observer mode and Full mode.
Observer mode gives you full analytics capabilities:
Integrations including attribution systems;
Integrating it usually takes under an hour, you'll only need to implement a couple of SDK methods. You can use Observer mode along with existing purchases infrastructure.
Full mode adds multiple features on top of Observer:
Complete purchases infrastructure: managing access to the app including lifetime, handling renewals, billing retries, subscription offers, grace periods, etc.;
Integration takes several hours, and in most cases, you should use Full mode as a complete solution for your app purchase infrastructure.